pitched roof

Our house is circa 1900, stone built. Top floor is converted. One bedroom is warm enough because it's a newer dormer, but the hallway and other bedroom are cold. Both mainly have a pitched roof. Both ceilings painted but one appears to be standard plasterboard, one Styrofoam and both are pretty...

I am planning to put a pitched roof on an existing ugly flat-roofed two-storey extension to my house. The extension is on the principal elevation and the propsed roof ridge will be lower than the original/main roof ridge. I assumed this was PD under Class B (Permitted Development) but am being...